Introduction to Desalination. Louis Theodore

and concentration of a substance.

       Chemical sludge – The sludge obtained by treatment of wastewater with chemicals.

       Chemical treatment – Any one of a variety of technologies that use chemicals or a variety of chemical processes to treat a system or waste.

       Chlorine demand – The amount of chlorine necessary to produce a free chlorine residual in a water sample.

       Chlorine water – A clear, yellowish liquid that degrades on exposure to air and light; it is employed as a deodorizer, disinfectant, and antiseptic.

       Clarification – The removal of suspended solids from wastewater by gravity settling; this process is often accelerated through coagulation of and flocculation of small solids with chemicals.

       Closed loop – A term used to describe an enclosed process.

       Closed loop cooling tower – Water-conserving cooling tower system in which water used for cooling is recycled through a piping system that cools the water.

       Coastal waters – The waters of the coastal zone, except for the Great Lakes and specified ports and harbors on inland rivers.

       Coastal zone – The lands and water adjacent to the coast that exert an influence on the uses of the sea and its ecology, or whose uses and ecology are affected by the sea.

       Coastline – The line separating the land surface and the water surface of the sea.

       Coliform – A group of related bacteria whose presence in water may indicate contamination by disease-causing microorganisms; indicators organisms of recent fecal contamination.

       Communicable disease – An illness that is caused by a specific infectious agent or its toxic products, and that arises through transmission from a reservoir to a susceptible host.

       Community water system – A public water system that serves at least 15 service connections employed by year-round residents or regularly serves at least 25 year-round residents.

       Condenser – Any device that cools gases or vapors to liquid.

       Conduit – Any artificial or natural duct, either opened or closed, employed for conveying fluids.

       Confined aquifer – An aquifer in which groundwater is confined under pressure.

       Confined groundwater – Water in an aquifer that is bounded by confining beds and is under pressure significantly greater than atmospheric pressure.

       Confining bed – A layer or mass of rock having very low hydraulic conductivity that hampers the movement of water into and out of an adjoining aquifer.

       Connate water – Water entrapped in the interstices of sedimentary rock at the time of its deposition.

       Conservative pollutant – A pollutant that does not decay, does not react, is persistent, and is not biodegradable.

       Contaminant – Any physical, chemical, biological, or radiological substance that has a harmful effect on human health or the environment when contained in air, water, or soil.

       Continuous sampling – The continuous withdrawal for analysis of a sample from some larger quantity of liquid, air, or solid.

       Cooling tower – A hollow, vertical structure, perhaps with internal baffles, to disperse water so it is cooled by flowing air and by evaporation at ambient temperature.

       Cooling tower makeup – Water added to a recirculating cooling tower water stream to compensate for water evaporation losses.

       Cooling water – Water typically used to cool heat-generating equipment or to condense gases in a thermodynamic cycle.

       Cooling water blowdown – The procedure used to reduce total dissolved solids by removing a portion of poor-quality recirculating water.

       Cooling water drift – Unevaporated water carried out of a cooling tower by the airflow; it has the same composition as the recirculating water.

       Cooling water evaporation – Cooling water recycling approach in which water loses heat when a portion of it is evaporated.

       Creep – The movement of water under or around a structure built on permeable foundations.

       Cryogenics – The production and utilization of extremely low temperatures.

       Crystallization – The change of state of a substance from a liquid to a solid by the phenomenon of crystal formation by nucleation and accretion (e.g. the freezing of water into ice).

       Deaeration – A process by which dissolved air and oxygen are removed from water.

       Decantation – The separation of a liquid from a solid or a higher density liquid with which it is immiscible by drawing off the fluid.

       Dechlorination – The removal of chlorine from a substance by chemically replacing it with hydrogen or hydroxide ions in order to detoxify the substances.

       Decontamination/detoxification – A process that converts toxic wastes into nontoxic compounds.

       Deep-well injection – A method of ultimate disposal that involves depositing liquid waste into a deep well beneath the surface of the Earth for permanent storage.

       Dehumidifier – A device incorporated into many air conditioning systems to dry incoming air by passing it across a bed of a hygroscopic substance or through a spray of very cold water.

       Dehydration – The chemical process where water in a chemical or material is removed.

       Deionized water – Common industrial water devoid of dissolved salts and organics, used to remove contaminants from products and equipment.

       Demineralization – The process of removing dissolved minerals from water by physical, chemical, or biological means.

       Demister – A device composed of plastic threads, wire mesh, or glass fibers employed to remove liquid droplets entrained in a gas stream.

       Desalination – The extraction of freshwater from sea or other salt water by the removal of salts, usually by evaporation, reverse osmosis, or crystallization.

       Desert – A terrestrial environment where evaporation exceeds precipitation, with consequent lack of vegetation.

       Detoxification – The destruction of the toxic aspects of a substance.

       Dew point – The temperature at which the first droplet of water forms on the progressive cooling of a mixture of air and water vapor; at the dew point, the air becomes saturated with water.

       Dialysis – The separation of smaller molecules from larger ones in a solution by means of the diffusion from a concentrated solution to a dilute solution across a semipermeable membrane.

       Discharge – The volume of water that flows past a given area in a given time.

       Dissolved solids (TDS) – Total dissolved solids, minerals, or salts in water.

       Disinfectant – Any substance that destroys harmful microorganisms or inhibits their activity.

       Disposal well – A well employed for the disposal of waste into a subsurface stratum.

       Dissolved oxygen (DO) – The oxygen freely available in water; it is one of the most important indicators of the quality of a water supply since oxygen is necessary for the life of aquatic organisms.

       Distillation – A process of separating the constituents of a liquid mixture by means of partial vaporization of the mixture and separate recovery of vapor and residue due to a difference of vapor pressure.

       Distilled water – A water of high purity, prepared by repeated distillation.

       Domestic